1. Field of the Invention
This invention relates in general to explosive formulations, more particularly to composite solid explosive formulations, and even more particularly to composite solid explosive formulations that fragment instead of detonating when subjected to a weak shock, but fully detonate when subjected to a strong shock. The present invention also relates to several applications of said explosive formulations. These incude composite solid explosives with an adjustable yield, thermobaric explosives, and explosives specifically tailored to chemically damage electronic equipment.
2. Description of the Related Art
In general, composite explosives are currently formulated by combining several components, all in powder form, but with at least one component capable of binding the others. In the case of pressed explosives, for example, a small fraction of wax or viton is added to the other energetic components and the mixture pressed. In the case of melt cast explosives, such as Composition B, made of RDX and TNT, the mixture is heated until the TNT melts, stirred, then slowly cooled until the TNT solidifies. In the case of plastic bonded explosives, the components of a polymer minus the curative are mixed with the energetic crystals then the curative added for cross-linking. The common feature among all of these explosive formulations is that the energetic materials are small particles, usually 100 microns or smaller, uniformly distributed throughout the explosive charge.
In a traditional fragmentation warhead, a metal shell usually surrounds the explosive core. When the explosive detonates, the high pressures generated fracture the metal and launch the resulting fragments at high velocity. However, in some warheads, pre-fragmented metal shrapnel are interspersed within the explosive itself. In some warheads the shell is not inert. U.S. Pat. No. 4,351,240 discloses a warhead comprising fragments arranged around the periphery of the warhead that are made of an incendiary metal material that ignites when heated sufficiently. U.S. Pat. No. 5,299,501 discloses a projectile composed of brittle material wherein the casing disintegrates upon impact and incendiary particles are propelled through a hole created in the warhead. But the explosive itself is made of small particles uniformly distributed throughout.
This uniformity of the explosive structure imposes limitations on its performance. For example, the explosive can be designed to accomplish a specific task, but only that task well. The particular chemical composition of the explosive is chosen from several candidates to perform the task best. If none of the candidates can alone perform the task well, several chemical compositions are uniformly mixed together in the same explosive. For example, an explosive charge mostly composed of HMX (Cyclotetramethylenetetranitramine) is good for fragmenting metal cases and driving the fragments at high velocity, but it will perform less than optimum in internal blast applications. That is because to drive fragments well, the explosive has to release a large amount of gases fast, but a good internal blast explosive has to be rich in fuels that react with the air contained inside the target, an intrinsically slow process. HMX and Al (Aluminum) particles can be uniformly mixed to create a good internal blast explosive, however, that would not be optimal for fragmenting metal and driving the fragments at high velocity.
Moreover, the traditional deign of a fragmenting warhead whereby the metal shell surrounds the explosive imposes limitations. The fragments are uniformly dispersed in all directions, thus only a small portion reaches the target. Attempts were made to improve the fragments pattern by still using one explosive material, but varying the shape of the explosive material or liners associated with the warhead along with a plurality of detonation points around and within the explosive material. For example, U.S. Pat. No. 6,393,991 discloses a multipurpose shaped warhead having a plurality of detonation points along the periphery of the explosive material and one detonation point in the center of the explosive material. U.S. Pat. No. 5,509,357 discloses a dual operating mode warhead having one explosive material with two different liners associated with two detonation points wherein detonating one of the points provides a certain output as a result of the liner associated with said point. U.S. Pat. No. 4,612,859 discloses a multiple purpose warhead having three different shaped explosives within a warhead, each having a different detonation point. Finally, U.S. Pat. No. 5,544,589 discloses a fragmentation warhead having multiple detonation points wherein selecting certain detonation points directs the fragments in a certain direction.
However, no explosive is currently formulated by consolidating macroscopic fragments, each fragment being itself a complete explosive formulation, instead of the traditional method of consolidating microscopic particles in which case by definition the particles are uniformly distributed throughout the resulting explosive. And no warhead design is currently capable of adjusting on demand the velocity of the fragments as well as optimally achieve substantially different outputs, such as high velocity fragments and a strong internal blast, simultaneously.